1. Field of the Invention
Aspects of the present invention relate to a battery pack, and more particularly, to a battery pack having an improved electrical coupling between a bare cell and a protection circuit module.
2. Description of the Related Art
Recently, compact and lightweight portable electronic devices, such as cellular phones, notebook computers, camcorders, etc., have been actively developed and produced. Portable electronic devices include a battery pack as a portable power source. A battery pack generally includes one or more secondary batteries.
Secondary batteries include nickel-cadmium (Ni—Cd) batteries, nickel-metal hydride (Ni—MH) batteries, lithium (Li) batteries, lithium ion (Li-ion) batteries, etc. Lithium ion secondary batteries have an operating voltage that is three times that of nickel-cadmium (Ni—Cd) or nickel-metal hydride (Ni—MH) batteries. In addition, the lithium ion secondary batteries have a higher energy density per unit weight.
Lithium ion secondary batteries use a lithium oxide as a cathode active material and a carbonaceous material as an anode active material. A secondary battery can include a liquid electrolyte or a polymer electrolyte. A lithium ion battery uses a liquid electrolyte, and a lithium polymer battery uses a polymer electrolyte.
A secondary battery pack includes a bare cell and a protection circuit module coupled to the bare cell. The bare cell includes an electrode assembly, an electrolyte, and a can to house the electrode assembly and the electrolyte. The bare cell stores and discharges electricity through a reversible chemical reaction. The protection circuit module protects the bare cell, by preventing the overcharging and over discharging of the bare cell.
In a conventional battery pack, the bare cell and protection circuit module are electrically and mechanically coupled to each other. In other words, an electrode terminal and a lead plate of the protection circuit module are connected to each other by welding or soldering, and then the lead plate is welded or soldered to the electrode terminal of the bare cell.
Accordingly, the welding or soldering process is performed several times during the assembly of the bare cell and protection circuit module. Thus, the assembly process is time consuming and complicated. In particular, the welding or soldering process lacks the precision that is required for producing a slim battery pack.